Pet sounds ... the frontman of Dead Cat Bounce, James Walmsley, is constantly having his vanity punctured by his bandmates. Photograph: Murdo Macleod

When you're watching someone on stage for an hour, particularly if they're standing there alone, you can't help but pay attention to what they look like. Comics are obviously aware of this, and for many their appearance or the way they present themselves is an integral part of their comedy.

In the course of watching many hours of comedy over many years, I've often wondered if being attractive is a hindrance to a comedian. As a general rule, in Hollywood – just as in school plays – the beautiful get cast as the romantic leads while the chubby, the bald and those with frizzy hair, geeky glasses or crooked teeth get the character parts. We're not programmed, it seems, to equate attractive with funny – which may explain why so many comics grow strange facial hair or choose weird clothes that help to cultivate a quirky physical appearance. This invites the audience, I suspect, to laugh at rather than fancy them.

I think attractiveness might be more of a disadvantage for women comics, perhaps because of the way women in the audience relate to them. In newcomers Ford and Akram's sketch show, Yasmine Akram makes a joke about having to leave Ireland because she was too good-looking to live there. It's a joke that's repeated several times in the show, with diminishing returns, because she genuinely is extremely beautiful, though an element of exaggerated arrogance is essential to the relationship with her double-act partner. By contrast, when Vikki Stone sings a song about how annoying a thin friend is when you're a slightly larger woman, the women in the audience of the show I was at were almost crying with laughter – presumably because this is a much more common experience to identify with. James Walmsley, frontman of comedy rock band Dead Cat Bounce, has all the raw sex appeal of a young Mick Jagger, and it's an important part of the group's dynamic that his bandmates are constantly puncturing his supposed vanity about his own rock-god image.

Perhaps it's a peculiarly British thing that we are suspicious of over-attractive comics. This might be because we enjoy the comedy of failure and self-deprecation, and find it hard to imagine that very good-looking people would share our own anxieties and insecurities.

When Nick Helm strips down to his pants in his show Dare to Dream, it signifies a moment of total despair, and the sight of a fat, sweating man in saggy Y-fronts prompts laughter that is mixed with pity. If he was buff, tanned and wearing designer underwear, the effect would be very different. A good comic wants to inspire empathy with the audience, not envy, and that is more easily achieved if a performer has an everyman or everywoman appearance.

In the end, it seems, we still like our clowns to look funny.

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